1. Field of the Invention
The present invention relates to apparatus and methods for guiding light from a light source, and in particular, to apparatus and methods for controlling and redistributing light from a relatively small light source or sources, or according to specific light pattern requirements.
2. Problems in the Art
Lighting applications, both required and elective, continue to increase and evolve. The nature of light energy many times allows multiple solutions to the same lighting goal. Therefore, although a lighting application can be generally defined, and there may exist one or more purported solution or solutions to reasonably meet the needed function, there is usually room for improvement in how the function is accomplished.
One example is in marine and automotive lighting. Government or industry regulations require running or safety lights, including for night-time or low light conditions. The regulations generally define the function of such a light, and perhaps at least some characteristics of the light output (e.g. intensity, uniformity, pattern, color).
The generation and/or manipulation of light can take many forms. A desired output can be defined, but there may be a variety of ways to achieve the output. Even for marine and automotive uses, there is no single light generation solution. One reason for this is the physics of light. For example, light energy can be produced in a number of ways. Current light source examples include, but are not limited to, incandescent, HID, and fluorescent. But each of these sources is available in different sizes, intensities, power ratings, etc. A further example is that light tends to disperse from the source, but can be controlled or manipulated by refraction, reflection, conversion, and other methods. On the other hand, light tends to lose energy during such manipulations.
But in addition to factors associated with the physics of light, practicalities in designing and implementing lighting applications must come into play in most situations. Examples include, but are not limited to, such things as constraints related to size, cost of production, cost of operation, energy consumption, safety, and complexity. Such issues are relevant to most marine and automotive lighting applications.
Therefore, as can be appreciated, most lighting applications present the opportunity for improvement because of the plurality of factors and variables involved. This allows for continued innovation and improvement in lighting solutions, even for what might be considered relatively non-complex lighting applications.
A very specific example in marine lighting is illustrative. A bow light, by regulation in the United States, must show a blue-green color on the starboard side and red pattern on the port side. One regulation requires that the blue-green and red lights must be in a specific pattern (basically rectangular—15 degrees in height total included angle, the centerline being horizontal; 112.5 degrees in width; with relatively sharp cut-off at the perimeter), have a minimum intensity (viewable to the naked eye from at least 1 or 2 miles away), and have a transitional area between green-blue and red in a precisely defined area (3 degrees wide, so that a viewer will normally see only blue-green or red, depending on relationship to the boat). The solution to these requirements, while staying within practical size, power, cost, and complexity limits, is not trivial.
For some time bow lights, and other safety or running lights for boats, have used incandescent bulbs and colored lenses. Incandescent fixtures in one sense are relatively economical, having the luxury of decades of development, and relatively high intensity for common commercial light sources. Again, however, it is not trivial to meet the specific requirements of, for example, a bow light such as articulated above, or to do so in an optimal way, balancing practicalities.
With regard to marine bow lights, light requirements are often given as a set of horizontally and vertically oriented points which define the required intensities at specific angles. Because these points are typically oriented on a rectangular coordinate grid, the resulting requirement is rectangular in angle space. In contrast, the typically non-rectangular light output of an unlensed light source is an inefficient pattern for meeting the requirements. In addition, marine lighting requires sharp cutoffs in the output intensity distribution to achieve light output requirements. This presents an additional set of problems with respect to design of a light, including a bow light, that meets industry standards.
In the bow light example, if an incandescent source is used, the incandescent light must be guided or controlled in a manner to conform to the rectangular output regulations. This usually requires lens(es) and/or reflectors which adds complexity and cost. Additionally, it is generally desirable that a bow light be as small as possible and low profile. Such strictures many times require compromises and/or additions to achieve the required light output.
There has been a need for improvement in bow lights and similar lights relative to incandescent fixtures using combinations of lens, reflectors, and colored filters. Attempts have been made. For example, several attempts to improve bow lights use light emitting diodes (LEDs) as the light source. Advantages of LEDs over incandescent sources include very low power consumption (e.g. 1.0 watt versus 5 to 10 watts for incandescent), robustness (good shock resistance), and very long life (20 K–100 K hours). But disadvantages include, among other things, higher cost and relatively narrow distribution pattern. Also, LEDs generally emit a conical light pattern if unlensed or unreflected.
Present LED based bow lights try to balance the advantages and disadvantages. One example uses a plurality (e.g. 7 to 10 LEDs for each side) of T 1¾ style LEDs with each LED source positioned at specific angles to generate overlapping conical output distributions which meet the bow lens lighting requirement. However, it is very difficult to achieve accurate alignment of each of the individual LEDs to meet the cutoff specification. This increases cost and quality variances in these products. Additionally, the design is wasteful of light energy at least on the vertical axis because the output of individual LEDs is usually conical and individual LED patterns must have significant overlapping to meet bow light output requirements. Further, the number of LEDs used and the optical structure required is significant in terms of cost to manufacture and operate.
Another example uses a custom manufacturing process to place LED dice directly on a circuit board. The dice are arranged in a linear pattern. Several high energy dice are used to create the required output intensity. This generates a very reliable cutoff point but the optical efficiency is poor. The number of sources results in a single “tall” source which forces the package size to be relatively large in the vertical direction as well as requiring significant power consumption, even for LEDs. Again, the substantial LED energy used and the other structure needed to produce the light output is significant in terms of manufacturing costs and operational costs.
Thus, a need exists in the art for improvement in bow lights and similar lighting. For example, there is a need for improvement in taking a spherical or conical output from a light source and efficiently manipulating it into a different pattern, including patterns that demand specified intensity gradients and relatively precise perimeter cut-offs. Other lighting application examples, both in and outside the marine and automotive fields, exist with similar issues and problems. As can be appreciated, similar or analogous issues exist for lighting applications other than automotive or marine related. A need also exists for improvement for such applications.